Chasing the Vizcacha – a day underground in the Teresita Mine, Central Peru

SouthAmerica January 28, 2017October 13, 2019 James M. Wise geologist, James Wise, Peru, south america, south america to the world, southamericatotheworld, southamericatotheworld.com, Teresita Mine

9-20-99

Early in the morning, standing on the front steps to the mine geology office at the Recuperada concentrator plant, I meet with the old Peruvian muestrero. His name is Silvester, or as his compañeros calls him, Silver. He speaks with a low, gravelly voice, and keeps a constant half smile for some secret. Señor Silver hands me a miner´s lamp and casco (hard hat), and then we load into the Toyota pickup to drive the two-kilometers up to the mine portals.

My chofer says, “¿Maestro, cuántos años trabajaste acá? [How long have you worked here?]”

Señor Silver jokingly replies, “Thirty two.”

Discounting Colonial Spanish workings, the Teresita vein, and other veins in the Huachocolpa district, started production around 1951. My guide for the day has been working here for most of that time, in jobs varying from watchman to the more recent position of ore control sampler.

At the 4,520-meter mine level, a group of mineros, clad in navy blue overalls, wait at the mine portal alongside ore carts on the narrow gauge rails. They are waiting for the air to clear from the seven o’clock blast. Señor Silver and I join them for the next twenty-minute wait. They all have many questions for me, and at times it is difficult to understand their language when spoken with wads of coca leaf puffing out of their cheeks like a group of squirrels at a picnic. I am a novelty for the day, and I have to think of several ways to decline their offers to trade for my rock hammer. As we talk, I wonder how many of the miners here remember another North American student who researched the Teresita vein in the early eighties- D. Bruha who graduated from the Mackay School of Mines, University of Nevada, Reno, in 1983. His economic geology study of the vein ran the course of petrology, fluid inclusions, and more important for my research, he analyzed muscovite from the vein, dating the mineralization at about 6.4 Ma. Other studies have looked at metal ratios and possible fluid flow directions for the Zn-Pb-Ag vein. Now I am following Señor Silver into the cross cut to search for the structural characteristics of the vein.

Our rubber boots slosh through the orange-tan mud along the tracks as we walk farther and farther into the mountainside. A trench cut along the side of the rails drains sluggishly flowing, orange, acidic mine water. A low growling echoes down the tunnel, soft at first, but steadily grows as an electric-powered motor hauls the metal mine carts loaded with ore. We press against the tunnel walls as the carts go by, and then continue our tour.

Upon reaching the vein, a series of galleries have been mined out along the vein overhead. The tunnel is framed in by round trunks of eucalyptus, and wooden chutes, protruding downward from the ceiling, are spaced at regular intervals in the tunnel. Once we reach the active face there are no more support timbers and the 1.5-meter thick vein defines a strip along the back. Lens-shaped pods of sphalerite and drusy quartz are sandwiched between anastomosing fault strands. The faults have 1 to 6 centimeters of gray gouge, as soft as Play Dough. We double back and then climb up a series of rickety wooden ladders inside a wood-framed chimney along the side of a chute. Above us a throbbing vibration of a jackleg can be heard, along with the hissing of thick black compressor lines and sounds of rocks being moved by pick and shovel. Climbing out of a square hole, where I have to fit my shoulders diagonal-wise to squeeze through, we come into an open slot along the vein. Señor Silver ducks beneath a beam, squeezes by several surveyors using a line and compass, and leads me along the gallery. A few measurements and sketches of the vein and fault surfaces, and then I am hurrying after my guide down a different chimney.

We return to the 520 level, and then walk a ways to another shaft. My headlamp shines down a narrow hole, wet with cascading acidic water, and filled by complicated confusion of thin wood ladders, platforms, and compressor lines. The first ten meters are wet, from a constant shower of orange water escaping the trench along the tracks. My guide looks at me and, without speaking, questions whether I want to continue.

“¡Vamos!”

He slips into the hole and scampers down the ladders. He seems to me a Vizcacha and like a hound I chase him down the hole. Vizcachas are an Andean resident, looking like a cross between a rabbit and a marmot with a long, curled, black tail added on as an afterthought. The comical animals live in holes on rocky slopes of the higher elevations of the Andes. Indeed, Señor Silver climbs down the shaft like a Vizcacha. I try to match his pace, but in the first five meters a narrow spot slows me down so that I may enjoy the acidic shower. Once out of the orange rain, and standing on a two by six inch plank, I take a moment to examine the slime coating the rock walls. Brown-orange sludge, rippled, wet, forming stalactites; it is both grotesque and fascinating. Now the Vizcacha is far below me so I take up the chase, climbing down fifteen ladders while thinking that I weigh more than the average Peruvian miner. If one of these ladder rungs snaps…let’s not go there.

At the 460 level we examine the working face, and then back track with my head craned upward to light up the vein overhead. At three locations I draw sketches of the vein, detailing the late-stage en echelon quartz veins, which give right-lateral sense of slip. At six different locations, the faulted margins of the vein have subhorizontal, southwest plunging, corrugations and striations in gouge. I feel rewarded for worming down the wet shaft, but on the return climb I seriously question the worth of the geological pursuit.

Again on the 520 level, I check out the Bodega de Explosivos. The miner working here is happy to explain to me the names in Spanish- fulminates is primer caps, guias are fuses, and dinamita, well, you get it!

Another long walk and again dodging ore carts brings us to the portal and the piercing blue sky. I blink with mole eyes at the whitish mine dumps and then strongly desire for a hot shower, a luxury that we do not have, and more importantly could use a cerveza. Fortunately, I have a six-pack of Heineken for such an occasion. If you think worming through a mine at 4,500 meters is hard work, try finding imported beer in Perú!